Influenza viruses and respiratory syncytial virus (RSV) remain important causes of morbidity and mortaility. The viruses affect host immunity in different ways both in vitro and in vivo, and represent useful probes for delineation of effective human immune responses. The long-term objective of these studies is to better define and understand effective human immunological defenses against viral pathogens, with eventual application to prevention or treatment of disease, e.g., via better vaccines or immunomodulatory therapies. The objective of this current project period is to define early, directive cell subpopulaitons as they arise from within the total human monoculear leukocyte pool in response to influenza virus and RSV. The specific aim of the project are: (1) to identify the active subpopulations as they arise from within the human totoal mononuclear leukocyte pool soon after in vitro exposure to each virus: (2) to establish that the active cell populations act as control elements of the total mononuclear leukocyte immune response toward each virus; and (3) for the two viruses, to compare the active, directive suboppulations, as established in (1) and (2), above, in addition to comparisons to control leukocyte populations. Analysis and comparison of standard samples, obtained by countercurrent centriugal elutriation (CCE) within a few days of exposure to influenza virus or RSV, will include cell cycle distribution determination protein synthesis assessment, and phenotypic characterization, using flow cytometry, gel electrophoresis, and scintillation counting. Subpopulations will be manipulated via CCE (removed, replaced; within homotypic and alternate responding leukocyte pools) and the consequent effects measured using established immunological assays. Assasy will rcongize cellular afferent recognition and proliferative activity (primed lymphocyte testing, and proliferation of homotypic and alternate anitgens) as well as soluble mediator production (interferon, interleukin-1). The entire research database is automated using Digital VAX/VMS information systems. A donor population typed for Class I and Class II HLA determinants help stratify results to reduce confounding variables. Thus, the project establishes a solid, functionally oriented (not phenotypically oriented), in vitro model to examine the early, integrated human immune response.